Cai2+ waves spread across individual hepatocytes in a polarized fashion. Although Ca2+ stores sensitive to IP3 are concentrated in the apical region, it is unclear whether Cai2+ waves begin apically; nor is it known which messenger molecules are responsible for Ca2+ release elsewhere in the hepatocyte. Increased Cai2+ also induces apical contractions in hepatocytes, which may be responsible for the peristaltic flow of bile that helps maintain secretion. However, the role of Cai2+ waves in regulating canalicular contraction also is unknown. This collaboration involves the optimization of multiphoton uncaging of NPE-IP3 for use in experiments designed to study the initiation and propagation of Cai2+ waves in hepatocytes.